Heat remaining 3 tablespoons oil in heavy large skillet over medium-high heat. Add remaining garlic clove; sauté until golden, about 2 minutes. Add clams and 1/4 cup water; cover and cook until clams open, about 5 minutes (discard garlic and any clams that do not open). Cool clams slightly; reserve pan juices. Working over bowl to catch juices, remove clams from shells; discard shells. Strain pan juices and clam juice from bowl into garbanzo bean mixture, then add 3 1/2 cups water and bring to boil. Add pasta and cook until pasta is just tender but still firm to bite, adding more water if soup is too thick and stirring occasionally, about 10 minutes. Stir in clams. Season to taste with salt and pepper.